King Henry wanted to considered invade Ireland. He wanted to give it to William. He held a council at Winchester in September, 1155 to discuss his plan. However, his mother Empress Matilda, objected because she did not think Ireland worth the trouble. William was given seven manors by King Henry II: Maldon in Essex, Dartford in Hoo, Shorne in Kent, Aylsham and Cawston in Norfolk, and Hintlesham in Suffolk. Land surrounding Dieppe, Normandy also was given to him & he was made Viscount there. This made him a very rich man.

William went with his brother, Henry, in 1156 to the siege of Chinon at the castle of Mountreuil-Bellay. It was brought about by the rebellion of Geoffrey, their brother. While carrying on, he had the writings of the Roman military rheorist 'Vegetius' read to him. He then did what Vegetius had done. The next day the siege ended.

William never married. However, a marriage to Isabel de Warenne, 4th Countess of Surrey, was arranged in 1162 . She was the widow of William of Blois (count of Boulogne and Mortain). He was the son of King Stephen of England, and a cousin of William. Isabel was one of the great heiresses in England. A dispensation from affinity was required so that the marriage could take place. These types of dispensations were normally granted. However, the archbishop of Canterbury, Thomas Becket, refused to grant it.

William was broken hearted and died shortly thereafter. He was buried in the Cathedral of Notre-Dame in Rouen.